As imaging devices represented by digital cameras have recently been reduced in size and weight, batteries loaded in the imaging devices have been formed in a rectangular parallelepiped advantageous in downsizing and weight saving. Imaging devices employing a battery need to be formed from a rigid member that withstands bending moment in order to prevent erroneous insertion of the battery or damage to the imaging device. This hinders the downsizing and weight saving.
To solve the problem, Japanese Patent Laid-open No. 2003-317689 shows a battery 14 as depicted in FIG. 14. This battery 14 is formed in a rectangular parallelepiped in which the length of an insertion-wise side is greater than that of a widthwise side to prevent erroneous insertion into an imaging device. In addition, an exterior package 140 of the battery is formed with notched portions 141 on its sides, which reliably prevents erroneous insertion and facilitates further downsizing and weight saving of imaging devices or the like attached with the battery 14. The exterior package 140 is provided with terminals 142 connected electrically to terminals of an imaging device attached with the battery 14. The number and positions of the notched portions 141 to be formed are determined so that an end face 143 is asymmetrical. On the other hand, a battery holder in the imaging device adapted to house the battery 14 therein has almost the same inner shape as the outer shape of the exterior package 14. In addition, the battery holder is formed with projections each of which engages a corresponding one of the notched portions 141, 141 when the battery holder is housed therein. Incidentally, Japanese Patent Laid-open Nos. Hei 11-307072, 2001-76700 and Hei 11-3692 disclose batteries of the same type as that disclosed in Japanese Patent Laid-open No. 2003-317689.
It has recently been requested to reduce the size and weight of devices such as imaging devices equipped removably with a battery, which has need to further downsize batteries. To further downsize the rectangular parallelepipedic battery, it is only needed to form the battery to have almost-square opposite surfaces. However, past batteries have no projections on lateral surfaces and the devices mentioned above have not clear retaining portions for retaining the battery received therein. For this reason, the users have not grasped the positional relationship between the battery and the retaining portions, leading to the high probability that the users erroneously insert the battery into the device mentioned above.
It is assumed that a battery is formed to have almost square surfaces and the respective terminal contacts of the battery and an imaging device are off-center. In this case, even if the battery is inserted upside down or laterally-erroneously inserted into the device, the terminals of the battery do not contact those of the device, that is, the battery does not electrically contact the device. However, a battery casing is liable to contact and damage the terminals of the device.
In view of the forgoing, the invention has been made and it is an aim of the present invention to provide a battery loading and unloading mechanism that can prevent erroneous insertion of a battery into a device resulting from downsizing of the battery attached removably to the device.